In recent years, as a power supply for a mobile electric device or electric power storage, a non-aqueous electrolyte secondary battery is in use, which employs a non-aqueous electrolyte and which is adapted for charging and discharging by way of transfer of lithium ions between a positive electrode and a negative electrode.
In such a non-aqueous electrolyte secondary battery, graphite material is in wide use as a negative electrode active material in a negative electrode. The use of graphite material has the following benefits. Since graphite material has a flat discharging electric potential and charging and discharging is performed by insertion and de-insertion of lithium ions among graphite crystals, generation of acicular metal lithium is prevented and volume change by charging and discharging hardly occurs.
On the other hand, in recent years, miniaturization and weight saving of mobile computing devices, such as a cellular phone, notebook PC, and PDA have been remarkably advanced. Further, power consumption has also been increasing associated with multi-functionalization. As a result, demand for miniaturization and weight saving in a non-aqueous electrolyte secondary battery used as these power supplies have been increasing.
However, the graphite material does not necessarily have a sufficient capacity and therefore is hard to sufficiently meet such demands.
Therefore, recently, the use of materials to be alloyed with lithium, such as silicon, germanium, and tin, has been examined as the negative electrode active material having a high capacity. Particularly, the use of silicon and silicon alloy as the negative electrode active material has been examined because silicon has a large theoretical capacity of about 4000 mAh/g.
However, in the case of using materials such as silicon to be alloyed with lithium, volume change associated with insertion and de-insertion of lithium is great and deterioration resulting from expansion during charging and discharging is caused. Further, materials such as silicon easily react with a commonly used non-aqueous electrolyte. Therefore, a negative electrode active material such as silicon is deteriorated by reaction between a non-aqueous electrolyte and itself, and there still remains a problem that charge-discharge cycle performances are lowered.
In this connection, as disclosed in patent document 1, there has been proposed a non-aqueous electrolyte secondary battery which comprises a negative electrode wherein a thin film of negative electrode active material containing materials to be alloyed with lithium is formed on the current collector and this thin film of the negative electrode active material is separated by gaps formed in the thickness direction into pillar shapes. Also, the parent document 1 has proposed to add carbonate compounds, particularly, a carbonate compound bonded with fluorine to a non-aqueous electrolyte solution used in the non-aqueous electrolyte secondary battery. Further, the patent document 1 discloses that, in such a non-aqueous electrolyte secondary battery, deterioration of the negative electrode active material by an expansion due to charging and discharging or by a reaction between a non-aqueous electrolyte and itself is suppressed.
In the patent document 2, there has been proposed to a battery using an electrolyte containing a diisocyanate compound having an aliphatic carbon chain. However, effects obtained by combination of the electrolyte and the negative electrode active material such as silicon have not been considered in the patent document 2.